Plotosus

Taxobox
name = "Plotosus"

---

image_caption = Striped eel catfish, "Plotosus lineatus"
image_width = 250px
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Siluriformes
familia = Plotosidae
genus = "Plotosus"
genus_authority = La Cepède, 1803
type_species = "Platystacus anguillaris"
type_species_authority = Bloch, 1794
subdivision_ranks = Binomial name
subdivision =
"Plotosus canius"
Hamilton, 1822
"Plotosus fisadoha"
Ng & Sparks, 2002
"Plotosus limbatus"
Valenciennes, 1840
"Plotosus lineatus"
(Thunberg, 1787)
"Plotosus nkunga"
Gomon & Taylor, 1982
"Plotosus papuensis"
Weber, 1910


synonyms = "Deportator" Gistel, 1848

"Plotosus" is a genus of catfishes (order Siluriformes) of the family Plotosidae. It includes six species, "P. canius", "P. fisadoha", "P. limbatus", "P. lineatus", "P. nkunga", "P. papuensis".cite journal|url=http://silurus.acnatsci.org/ACSI/library/biblios/2007_Ferraris_Catfish_Checklist.pdf|title=Checklist of catfishes, recent and fossil (Osteichthyes: Siluriformes), and catalogue of siluriform primary types|first=Carl J., Jr.|last=Ferraris|journal=Zootaxa|volume=1418|pages=1–628|year=2007|format=PDF]

Distribution

"P. canius" originates from coastal regions of Thailand, Sundaland, Sulawesi, Moluccas, and India, and into the lower Mekong River. "P. fisadoha" is known only from Southeastern Madagascar. "P. limbatus" inhabits marine and brackish waters in the Western Indian Ocean and Arabian Sea. "P. lineatus" occurs in the eastern Mediterranean, marine waters in the Indian Ocean and Western Pacific, and sometimes entering freshwaters in East Africa and Madagascar. "P. nkunga" is distributed in southern Africa from Boknes to Boteler Point, and possibly to Zanzibar, in marine waters but also entering freshwater. "P. papuensis" ranges in southern New Guinea island.

Description

"P. canius" reaches the largest size, up to 150 centimetres (59 in) TL. "P. limbatus" grows to 41 cm (16 in) SL. "P. lineatus" grows to 32 cm (13 in) TL. "P. nkunga" grows to about 51 cm (20 in) SL. "P. papuensis" is recorded to reach 55 cm (22 in) TL, though it may reach 100 cm (40 in) TL according to local fishermen.

All species have been confirmed to be venomous except for "P. fisadoha". The anterior spines of the dorsal and pectoral fins can inflict painful wounds. In "P. lineatus", the highly venomous serrate spine of the first dorsal and each of the pectoral fins may even be fatal.FishBase species|genus=Plotosus|species=canius|year=2007|month=Aug] FishBase species|genus=Plotosus|species=fisadoha|year=2007|month=Aug] FishBase species|genus=Plotosus|species=limbatus|year=2007|month=Aug] FishBase species|genus=Plotosus|species=lineatus|year=2007|month=Aug] FishBase species|genus=Plotosus|species=nkunga|year=2007|month=Aug] FishBase species|genus=Plotosus|species=papuaensis|year=2007|month=Aug]

Ecology

"P. canius" is found mostly in estuaries and lagoons, and sometimes up rivers in nearly fresh waters. It occurs in the lower parts of rivers in freshwater or brackish water and in coastal seas. "P. limbatus" occurs in estuaries and along open coasts. "P. lineatus" is the only catfish found in coral reefs; it is also found in estuaries, tide pools and open coasts. "P. papuensis" is found in turbid rivers and swampy lagoons and backwaters.

Juveniles of "Plotosus" species often form dense aggregations; in "P. lineatus" juveniles form dense ball-shaped schools of about 100 fish, while adults are solitary or occur in smaller groups of around 20 and are known to hide under ledges during the day..

Most species feed on crustaceans, mollusks, and fishes. Adult "P. lineatus" search and stir the sand incessantly for crustaceans, mollusks, worms, and sometimes fish. "P. nkunga" feeds mainly on benthic invertebrates.

"P. lineatus" is an oviparous fish; this species has demersal eggs and planktonic larvae.

Physiology

Interestingly, unlike the freshwater "Siluriformes" from which it evolved, "Plotosus" has evolved long ampullary canals in its electrosensory organs (originally termed "ampullae of Lorenzini", though now the name is not used) as the voltage gradient across the skin is less than in fresh water and so they must extend deeper into the fish where the difference will be more marked in order that the maximal volatage be registered. Such deep canals are found in elasmobranchs, though not in the freshwater stringray "Potamotrygon", indicating this time "loss" of extended canals rather than gain.

References